Solid ink jet printers were first offered commercially in the mid-1980's. One of the first such printers was offered by Howtek Inc. and used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings that fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends with separate rounded, five, six, and seven sided shapes each corresponding to a particular color.
Later more successful solid ink printers, such as the Tektronix Phaser.TM. III, the Tektronix Phaser.TM. 300, and the Jolt printer offered by Dataproducts Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed chute and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. One system utilized an ink stick loading system that initially feeds the ink sticks into a preload chamber and then loads the sticks into a load chamber by the action of a transfer lever. These ink stick feed systems melted the entire supply of ink, requiring all of the molten ink to be kept at an elevated temperature for extended periods of time to maintain the molten state, thereby tending to cause the molten ink to degrade over time from being maintained at the elevated temperature. Earlier solid or hot melt ink systems also used a flexible web of hot melt ink that is incrementally unwound and advanced to a heater location or employed vibratory delivery of particulate hot melt ink to the melt chamber.
As phase change ink color printers have increased their printing speed the need has developed to provide larger sized ink sticks so that refill of the ink reservoir in the print head is less frequent and more output or prints can be produced between refills. In designs where there is not a steep or generally vertical feed path to the heater plate, some provisions have been made to prevent the solid masses of shaped ink from sticking to the sides of the feed chutes so that an unrestricted feed of ink sticks proceed down into the heater plate for melting and filling of the individual colored ink reservoirs that are usually located within the print head. These larger sized ink sticks are fed into receptacles or openings in a cover plate over the feed chutes. If an ink stick is inadvertently inserted within the wrong receptacle it can be difficult for the printer operator to remove the ink stick, especially because of the sticky nature of the ink sticks' waxy exterior surfaces that can cause them to become wedged in the incorrect ink stick receptacle. There is a need to provide an effective and efficient way to feed a plurality of ink sticks in an ink stick feed bin to melt plates for melting to feed molten ink into the individual colored ink reservoirs. There is also a need to feed only the amount of molten ink that is needed for printing, or to melt the solid ink on demand.
These problems are solved in the design of the present invention by providing an improved solid ink stick loading system and that guides a plurality of solid ink sticks down a plurality of individual ink stick feed chutes to heated melt plates which melt the lead solid ink sticks in each ink chute and deliver the melted ink to individual colored ink reservoirs where the ink is maintained in a heated state until jetted by the print head.